1. Field
The present disclosure is directed to wireless communication devices. More particularly, the present disclosure is directed to a method and apparatus for radio link control padding compatible with turbo codes and Chase and incremental redundancy combining.
2. Introduction
Wireless communication devices used in today's society include mobile phones, personal digital assistants, portable computers, and various other electronic communication devices. New wireless technologies are continually being developed to support increasing demands for better reliability during voice calls, for improved throughput during Internet and other data connections, and for other desirable features. These new wireless technologies are often designed to accommodate older wireless technologies so users of older wireless communication devices can still use their devices on newer networks and, conversely, so that users of newer wireless communication devices can use their devices on older networks.
Unfortunately, such backward compatibility may hinder the full potential of new wireless technologies. For example, an older mobile phone using an older technology, such as Enhanced General Packet Radio Service (EGPRS), may operate on the same channel as a newer mobile phone using a newer variant of EGPRS technology, such as Enhanced General Packet Radio Service 2-B (EGPRS2-B). To ensure proper communications for the older EGPRS mobile phone, however, the newer EGPRS2-B mobile phone may be forced to use the older EGPRS technology for its communications and may accordingly experience reduced performance. Such is the case when both an EGPRS mobile device and an EGPRS2-B mobile device are assigned to a same uplink time slot by a base station serving both mobile devices.
There have been proposals for multiplexing EGPRS2-B mobiles with EGPRS2-A mobiles and EGPRS mobiles on the same uplink time slot. Currently, at least two methods have been proposed for multiplexing EGPRS2-B and EGPRS2-A mobiles. Specifically, when simultaneously sending data to the EGPRS2-B mobile and USF to the EGPRS2-A mobile, the network could either: (i) use MCS-2 or MCS-3, in accordance with the radio link control (RLC) family in use when not transmitting uplink state flag (USF) information to the EGPRS2-A mobile; or (ii) use only EGPRS2-A modulation and coding schemes within the TBF whenever the EGPRS2-B mobile is multiplexed with an EGPRS2-A mobile in the same uplink time slot. These same two options exist for an EGPRS2-B mobile that is multiplexed with an EGPRS mobile in the same time slot.
However, there is an additional restriction on (ii) that only DAS-5, DAS-6, or DAS-7 can be used when simultaneously sending data to the EGPRS2-B mobile and USF to the EGPRS mobile.
Both of the above proposals have significant deficiencies. The use of (i) is unattractive as the data rates of MCS-2 and MCS-3 are very low (11.2 and 14.8 kbps, respectively) and the RLC block must be split over multiple radio blocks. Further, neither incremental redundancy nor Chase combining can be used to combine MCS-2 and MCS-3 retransmissions of RLC blocks with previous transmissions using DBS 5-12. Likewise, the second proposal (ii) is unattractive in that it reduces the peak achievable rate from 118.4 kbps for DBS-12 to 98.4 kbps for DAS-12. Furthermore, the throughput as a function of signal-to-noise ratio is somewhat better for the DBS modulation and coding schemes than it is for the DAS modulation coding schemes, and this performance disparity will increase in the event that a second wider bandwidth pulse shape is standardized for or implemented in EGPRS2-B.
In GERAN #36, there was a proposal to allow the EGPRS2-B mobile to switch between EGPRS2-B and EGPRS2-A modulation and coding schemes within the Temporary Block Flow (TBF). And expanding, it was suggested that both DAS 5-12 and EGPRS modulation and coding schemes MCS 5-9 could be allowed within the EGPRS2-B TBF. Disadvantageously, however, Chase and incremental redundancy combining is not currently possible between radio blocks encoded using MCS 5-9 and radio blocks encoded using DAS and DBS modulation and coding schemes.
In order to improve the uplink state flag (USF) multiplexing efficiency between EGPRS2-B and EGPRS2-A and/or EGPRS, it would be desirable that, whenever possible, turbo codes and incremental redundancy HARQ be supported when signaling USF information to the EGPRS2-A or EGPRS mobile within the EGPRS2-B TBF. Towards this end, it is proposed in this disclosure, that new padded modulation and coding schemes DAS-7 pad, DAS-10 pad, and DAS-12 pad be defined and implemented within the EGPRS2-B TBF. These modulation and coding schemes are compatible with HARQ and can be efficiently multiplexed with DBS-6, DBS-10, and DBS-12. Furthermore, these new padded modulation and coding schemes add minimal additional complexity to the EGPRS2-A and EGPRS2-B mobiles.
Thus, there is a need for methods and apparatus for providing improved performance when a newer, backward-compatible wireless device, such as EGPRS2-B, a less capable, non-forward-compatible wireless device, such as EGPRS2-A, and an older, non-forward-compatible wireless device, such as EGPRS, must co-exist and interoperate in a system.